Method _calculateParents

src/cdk/tree/tree.ts:1126–1148

Traverse the flattened node data and compute parents, levels, and group data.

(flattenedNodes: readonly T[])

  /** Traverse the flattened node data and compute parents, levels, and group data. */
  private _calculateParents(flattenedNodes: readonly T[]): void {
    const levelAccessor = this._getLevelAccessor();
    if (!levelAccessor) {
      return;
    }

    // clear previously generated data so we don't keep end up retaining data overtime causing
    // memory leaks.
    this._clearPreviousCache();

    for (let index = 0; index < flattenedNodes.length; index++) {
      const dataNode = flattenedNodes[index];
      const key = this._getExpansionKey(dataNode);
      this._levels.set(key, levelAccessor(dataNode));
      const parent = this._findParentForNode(dataNode, index, flattenedNodes);
      this._parents.set(key, parent);
      const parentKey = parent ? this._getExpansionKey(parent) : null;

      const group = this._ariaSets.get(parentKey) ?? [];
      group.splice(index, 0, dataNode);
      this._ariaSets.set(parentKey, group);
    }
  }

  /** Invokes a callback with all node expansion keys. */
  private _forEachExpansionKey(callback: (keys: K[]) => void) {